Electromagnetic friction clutch



April 17, 1951 E. D. LILJA ELECTROMAGNETIC FRICTION CLUTCH Filed Aug. 151, 1945 INVENTOR Edgar D. Lil 'a BY c i I I r @FTORNEYS if Patented Apr. 17, 1951 ELECTROMAGNETIC FRICTION CLUTCH Edgar D. Lilja, Rockford, Ill., assignor to Barber- Colman Company, Rockford, 111., a corporation of Illinois Original application January 13, 1943, Serial No. 472,265.. Divided and this application August 31, 1945, Serial No. 613,718

'8 Claims. (o1. 192 -s4) This invention relates to clutches in which driving and driven elements are brought into frictional gripping engagement by energization of an electromagnet and more particularly to those in which the magnet coil and part of the magnetic flux circuit are stationarily mounted.

One object is to provide a clutch of the above character which permits the use of a driven element of extremely low moment of inertia.

A more detailed object is to provide a clutch of the above character in which the driven element is a thin disk adapted to be gripped between twodriving elements when the clutch magnet is energized.

The invention also resides in the novel arrangement of the parts which permits the reluctance of the non-ferrous parts of the magnetic flux circuit to be maintained uniform at all times.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a perspective view of the improved clutch broken away to show the parts in radial section. N

Fig. 2 is a perspective view of the driven clutch disk.

The invention is shown in the drawings embodied in a clutch for transmitting rotary motion from a driving gear 5 to a driven shaft 6 onwhich the gear is rotatably supported. The driven clutch element is of low moment of inertia and comprises a thin disk I of metal such as stainless steel having a hub 8 splined on the shaft 6 and, if desired, covered with thin rings 9 of friction material such as cork.

In accordance with the present invention, the driven clutch disk is adapted to be gripped between two plates l and II upon energization of a stationarily mounted magnet ring I2 concentric with the shaft 6. The magnet ring is of U-shaped cross section and provides two iconcentric pole pieces 13 and I4 between which is disposed a coil [5. A flange l6 projecting from the outer pole piece may be mounted on any suitable stationary support (not shown).

The magnetic plate I0 is in the form of a flange integral with and projecting outwardly from a sleeve ll to which the drive gear is fixed and in which the shaft 6 rotates. The sleeve is journaled in bearings I 8 supported by the magnet ring I 2 and holding the plate In in fixed axial position. The sleeve IT has a free running fit at IS with the inner pole piece [4 of the magnet ring, and the outer portion of the plate it has a similar fit 20 with the outer pole piece it. The plate It is composed of inner and outer magnetic parts 2! and 22 separated by a non-magnetic central portion 23 and constituting extensions of the magnet pole pieces [3 and I4.

Thus, the magnetic parts 2| and 22 and the pole pieces 13 and i4 cooperate to form annular pole members. The plate H has a running fit with the hub 8 of the driven disk 1 and is slidably connected with the plate 10 through keys 24- extending across the outer periphery of the disk 1 and connected by screws 25 to the ring 22. Leaf springs 26 anchored on the plate II are connected to the keys and urge the plate axially toward the plate l0 so as to maintain the driven disk in light mechanical contact with both of the plates it] and II.

The magnetic plate I I thus completes the magnetic flux circuit indicated in the dotted outline (Fig. hand extending from the outer pole piece 53 through the ring 22, the armature plate I l, and the inner ring 2! to the inner pole piece [4. It will be observed that, since the plates are urged together axially, the reluctance of the flux circuit remains constant at all times so that the degree of gripping engagement of the driven disk is always proportional to the degree of energization of the coil 55. When such energization takes place, the plates Ill and II are attracted toward each other, and the driven disk is thereby gripped frictionally between them so that the clutch transmits a torque corresponding to the energization of the coil I 5.

This application is a division of my copending application Serial No. 472,265, filed January 13. 1943, now Patent No. 2,386,402.

.I claim as my invention:

1. An electromagnetic friction clutch comprising a stationarily mounted magnet ring having concentric annular pole pieces and a coil disposed therebetween; said pole pieces providing axial facing ends, a plate rotatable about the axis of said annular pole pieces and having inner and outer magnetic portions lying adjacent the respective pole ends and magnetically separated radially from each other, a second plate of magnetic material rotatable with said first plate and yieldably urged axially toward the latter, a shaft rotatable about said axis, and a relatively thin disk fast on said. shaft and disposed between said plates, said magnet, said second plate, and the inner and outer portions of said first plate forming a magnetic flux circuit of uniform reluctance around aid coil and through said disk.

2. An electromagnetic friction clutch-comprising a stationarily mounted magnet ring having concentric pole pieces and a coil disposed therebetween, said poles providing axially projecting concentric pole pieces and acoil disposed therebetween, said poles providing axially projecting.

ends, two rotatably mounted magnetic disks disposed opposite said pole. ends and completing a said disks being shiftable axially relative to each other, and a thin rotatable disk disposed betweensaid first disks and frictionally gripped therebetween when said magnet coil is energized.

4. An electromagnetic clutch having, in combination; a stationarily mounted magnetring having concentric. annular pole pieces and-a coil! therebetween a driven disk rotatably mounted between the ends of said pole pieces to turn about the axis of said pole pieces, amagnetic memberdisposed between said disk and'said pole pieces, a second magnetic member disposed on the opposit'eside of said disk, said members forminga magnetic flux circuit extending from one pole" pieceto the other through said disk, means rotatably supporting said first member in fixed relation to said pole pieces, and means extending across the outer periphery of said disk and sup-' porting said second member for axial movement toward and away from said first member.

5. An electromagnetic friction clutch comprising a stationarily mounted magnet ring having concentric pole pieces with a common axis and a coil disposed therebetween, a plate rotatable about said axis and having inner and outer magnetic portions lying adj ace'nt' the respective pole. pieces" and magnetically I separated radially from each other, a second plate of magnetic material rotatable with said first plate and yieldably urged axially'towardthe'latter, a shaft rotatable" about aid axis, and a relatively thin" disk dis-- posed'between'sai'd plates, said magnet'ring, saidsecond plate, and the inner and outer' portions of said first plate'forming a magnetic flux circuit of uniform reluctance extending around said coil and through said disk.

6. An electromagnetic friction clutch comprising an annular magnet having annular: pole members concentric with the axis of the mag-- net and a coil, said pole members providing flat axially projecting ends magnetically separated radially from each other, a plate of magnetic material rotatable about aid axis: and radially magnetic circuit from one pole end to the other,

V 4 spanning said pole ends, spring means yieldably urging said plate axially toward said pole members, a shaft rotatable about said axis, and

a relatively thin disk of nonmagnetic material disposed between said plate and said pole ends, said plate cooperating with said magnet to form a magneticzfiux circuit extending back and forth through said disk whereby tocause the latter to be gripped between said plate and said pole ends when said coil is energized.

7--An electromagnetic friction clutch comprising an annular magnet coil, a stationarily mounted magnetic ring partially surrounding each cross-section of said coil, a radially disposed friction plate composed at least in part of magnetic material and disposed at one end of; said c0il,, means rotatably supporting said plate: to tum about the coil axis, a second radially, disposed friction plate supported adjacent'sa'id first plate for rotation about said axis, and a magnetic plate disposed on the other side of said friction plate and cooperating with said magnetic ring and .said' firstplate to formamagnetic flux path extending axially across said second plateand' acting when said' coil is energized to' draw said three plates into grippingengagement.

8; An electromagnetic clutchhaving, in combination, a stationarily mounted magnet ring having concentric annular pole pieces and a coil 7 plurality of angularly spaced parallel barseach rigid at one end with said first member and projecting across the outer periphery of" said disk, and radial arms projecting inwardly'f-rom the projecting ends of saidhbars and supporting said second magnetic member for axial floatingmovement toward and away'fromsaid firstm'em ber.

EDGAR D. LILJA.

REFERENCES" CITED The following, references-are ofrecord in the:

file offtlfiisv patent:

UNITED STATES PATENTS Number Name Date 736,789 Schuster' Aug. 18, 1903 1,342,270- Walker June 1'', 1920 1,823,334 Payne Sept. 15, I931 FOREIGN PATENTS Number Country Date" Great Britain Oct; 4, 1923: 

